1. Field of the Invention
This invention relates to novel polyols and to processes for their preparation and is more particularly concerned with novel phosphorus-containing polyols and with processes for their preparation and with their use in the preparation of fire retardant foams.
2. Background of the Invention
A prodigious amount of research has been devoted in recent years to the development of phosphorus-containing compounds which possess active hydrogen containing groups such as hydroxyl and amino and which can, therefore, be incorporated chemically into polyurethane and like polymers. The incorporation of such phosphorus containing compounds into polymers generally results in some degree of enhancement of the flame retardant properties of the polymer. However, many of the phosphorus containing compounds so investigated have proved to be of no practical importance because of undesirable side effects such as an adverse change in physical properties of the resulting polymer, incompatibility with the other components of the polymer forming mixture, and the like.
One of the more successful groups of phosphorus compounds of the above type, which has been developed and widely used in imparting fire retardance to polyurethane foams, is that represented by the formula: ##STR1## within this group the compound diethyl N,N-di(2-hydroxyethyl)-aminomethylphosphonate is widely known and used commercially; see U.S. Pat. No. 3,076,010.
Unfortunately, this compound and the class to which it belongs share a disadvantage which is common to many other potentially useful phosphorus containing polyols in that they are unstable when stored for extended periods of time in combination with other components normally employed in the fabrication of polyurethanes. It is common practice to supply two component systems for the manufacture of polyurethanes, one component being a polyisocyanate or an isocyanate-terminated prepolymer, and the second component being a mixture of polyols, surfactants, catalysts, and the like additives. The two components are stored separately until it is desired to produce the desired polyurethane at which point the two components are mixed and allowed to react.
When a phosphorus containing polyol, such as the particular ones discussed above, is to be employed in a two component system for the production of polyurethanes, it is desirable to include it as part of the component which contains the polyol and other ingredients. Obviously, the phosphorus-containing polyol cannot be incorporated in the polyisocyanate component because of the interaction which would take place. It is, therefore, desirable that any phosphorus polyol which is to be employed in the above manner be stable when stored in admixture with the polyol and other ingredients of the polyol component. It is an object of the invention to provide a phosphorus-containing polyol which meets this criterion and which is also capable of imparting fire retardant properties to polyurethanes without exerting any deleterious effects on the physical properties of the latter. Other objects of the invention will become apparent as the description of the invention proceeds.
Many compounds closely related chemically to the known compounds of formula (I) above have been described in the art. Illustratively, U.S. Pat. No. 3,314,957 shows bis(dialkylene glycol) dialkylaminomethanephosphonates and related compounds and their use in the synthesis of polyurethanes. Substantially the same group of compounds is also disclosed in U.S. Pat. Nos. 3,549,728, 3,457,333 and 3,539,536 both show the corresponding bis(hydroxypolyalkoxyalkyl) N,N-di(hydroxyalkyl)aminomethanephosphonates and their use in the synthesis of fire retardant polyurethanes. U.S. Pat. Nos. 3,480,594 and 3,480,699 show O-(hydroxyalkoxy)-O'-hydroxyalkyl N,N-di(hydroxyalkyl)aminomethanephosphonates and fire retardant polyurethanes derived therefrom. U.S. Pat. No. 3,567,801 shows generically, but not specifically, di(hydroxyalkoxy) aminomethanephosphonates in which the two nitrogen atoms can be unsubstituted. U.S. Pat. No. 3,707,587 is concerned with a process for preparing, inter alia, di(hydroxyalkyl) N,N-di(hydroxyalkyl)aminomethanephosphonates by reacting dialkanolamines with spirocyclic phosphorus compounds obtained, for example, by reacting alkylene-1,2-glycols with trialkylphosphites.
We have now found that a certain narrow class of esters of N,N-disubstituted aminomethanephosphoric acid possess properties which are highly advantageous and which distinguish them from the many such esters of this class hitherto known.